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Topic: naked eye equivalent? (Read 10212 times)

I can't seem to find the answer to my question, which is what lens could I buy for my T4i (or any crop camera) that would give me an equivalent to what the naked eye sees? 24mm? 35mm? Sorry if this has been asked a million times but I'm just curious. I recently got a 50mm, 1.8, and am loving it. I wish my camera had come with this lens! But it has gotten me curious about other prime lenses and I want one that's close to the naked eye.

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You might well hear different but as far as I know 50mm is pretty close to normal human vision.

50mm focal length is 50mm focal length as long as the lens matches the mount on your camera; Your EF 50mm f/1.8 on a Rebel will look like about 80mm because the Rebel has a smaller sensor. If you have an 18-55 you could set it to 50mm and compare it to the results from your 50mm f/1.4.

It's generally considered that a 50mm on FF gives the same prospective as our vision, ie the magnification of the scene from a given distance, but the 35mm is closer to our conscious field of view. However some suggest that when we concentrate on an object close to us our prospective in lens terms becomes more like 85mm.

In APS-c these become 32mm, 22mm and 54mm. They translate directly because they provide the same field of view as FF and as prospective is a result of distance it is the same with these lenses.

But it becomes more complicated as people often don't realise that we do not 'see' with our eyes, it is our brain which 'sees', our eyes are just like the lens on the camera. This is why a camera will never be able to really match what we can see in one exposure; we are seeing the world in what is in photographic terms a combination of HDR and focal length and focus stacking !

As standards go, one can arbitrarily subscribe to either a" wide" or "normal" standard...very lose terms that are filled by the 35mm and 50mm respectively in the full frame world. The "real" normal would actually be a ~42mm for which there was no prime in the Canon full frame lens pantheon....until they released the EF 40mm pancake.

But you are lucky as in the crop field you actually have several primes that will fit all three slots....just pick one.

50mm focal length is 50mm focal length as long as the lens matches the mount on your camera; Your EF 50mm f/1.8 on a Rebel will look like about 80mm because the Rebel has a smaller sensor. If you have an 18-55 you could set it to 50mm and compare it to the results from your 50mm f/1.4.

To get the FoV that a 50mm gives on FF, use an EF-S 18-55 at 31mm. An 18-55 @50 gives an identical FoV as a 50/1.4 if they're both on a crop body.

In terms of primes, somewhere in the region of 28-35mm is close to that 31mm to give equivalent FoV of a 50mm on FF.

However, the human field of view is said to be nearer to a lens with a focal lens equal to the diagonal of the sensor - 50mm lenses are cheap and easy to manufacture, and very close to this length, hence their popularity - but 43mm on FF is the nearest match to the human eye. Which makes something close to 27mm lens on crop ideal.

The human eye(s) do not see uniformly. We can see almost like a fisheye lens http://en.wikipedia.org/wiki/Human_eye#Field_of_view. The quality of the periphery though is extremely poor by photography standards. It quickly degrades from the center, actually. We see by scanning the scene.

The "standard" AOV/FL is usually accepted to be somewhere between 40mm and 50mm on FF but there cannot be exact definition (despite what wikipedia claims). If you want to replicate a portion of what you see, you need to measure the width of the picture on your monitor at a typical viewing distance, and the distance to it. If that picture is, say 36cm wide, and you view it from 45cm, then you need a 45mm equivalent lens. Not that any other lens will produce poor images.

The "standard" AOV/FL is usually accepted to be somewhere between 40mm and 50mm on FF but there cannot be exact definition (despite what wikipedia claims).

The frame diagonal is the standard used by photographers since the beginning of time. I learned this rule way back in the 1960s, well before anyone thought of starting Wikipedia. People were using a 150mm as a standard lens for 4x5 well before Oskar Barnack inverted the 24x36mm still film camera.

The frame diagonal is the standard used by photographers since the beginning of time. I learned this rule way back in the 1960s, well before anyone thought of starting Wikipedia. People were using a 150mm as a standard lens for 4x5 well before Oskar Barnack inverted the 24x36mm still film camera.

And what is the rational behind this "rule"?

BTW, 150mm on 4x5 is about 8.4% below the "standard" 163mm; like 39.9mm on FF.

honestly, i've never really understood this. my vision is nothing like a 50, 43, or 35mm lens. more like a fish eye, that i scan around in with a varying area of focus. i'm sure what i'm not actually focusing on is a complete mess but my brain is pretty damn good at filling in the pieces, and getting right what it needs to get right. now that i think about it, it could be a method to ease the brain's workload to fight off fatigue. like the way a racer/ fighter jet pilot let's go of everything they see around them that they don't need.

First, as others have noted, the human visual system has a field of view approaching 180°, but acuity is limited to a very small central region. There's actually an excellent XKCD devoted to the subject.

The photographic definition of a "normal" focal length being equal to the diagonal of the sensor / film format has much more to do with perspective than anything else. It just so happens that a comfortable viewing distance varies with image size, such that you tend to preserve the same angle of view regardless of print size. That is, you'll stick your nose in a 4" x 6" print, you'll look at an 8" x 10" print from normal reading distance, you'll stand back to look at a 24" x 36" print, and you'll look at that billboard from a block away.

And, at that typical viewing distance, the perspective of a normal focal length lens is such that it pretty much matches the same perspective the photographer saw. That is, if you're using a normal lens, if you make an instant 8" x 10" print right there and hold it in front of you at reading distance, the print is going to match up very closely with the original scene.

You know how wide-angle lenses tend to give a distorted perspective? Well, stick your nose in the print, and it suddenly doesn't look so distorted. Same thing with telephoto lenses and their compression; stand back a ways, and it looks quite normal.

So...short version, is, there is no camera that duplicates human vision. Cameras and eyes are two radically different imaging systems. Each can do things the other can't.

I would, however, encourage you to spend a lot of time experimenting with the matter. Pick some sort of still life and get really friendly with it. Shoot it from all different positions with all different lenses -- anything and everything you can get your hands on, even if only by borrowing and / or renting. Shoot at different apertures, while you're at it. And, most importantly -- though you might not realize it right now -- play with the light. Just a couple cheap task or work lights, a bulb with a reflector, will do -- and extra bonus points if you can dim them. Move the lights all around the scene as you move around the scene.

The purpose of this exercise, of course, isn't to create great art. Rather, it's to get a visceral, hands-on understanding of what the relationship is between perspective and position and focal length and how light plays together and all that stuff. Don't worry...once you see some of these things, you'll have more than one "ah-HA!" moment, and that'll inspire you to go do something truly creative.

Cheers,

b&

P.S. Your homework assignment: find out the actual dimensions of your camera's sensor, including the diagonal. It's in the manual and on the manufacturer's Web site, along with other places. Then, cut a hole in a piece of paper the same size as said sensor. Now, hold that paper up to your eye. Have a ruler handy so you can see how far the cutout is from your eye, and compare with the numbers on your camera's lens. b&

The approximate field of view of an individual human eye is 95° away from the nose, 75° downward, 60° toward the nose, and 60° upward, allowing humans to have an almost 180-degree forward-facing horizontal field of view.[citation needed] With eyeball rotation of about 90° (head rotation excluded, peripheral vision included), horizontal field of view is as high as 270°. About 12–15° temporal and 1.5° below the horizontal is the optic nerve or blind spot which is roughly 7.5° high and 5.5° wide.[6]

In photography and cinematography a normal lens is a lens that reproduces a field of view that generally looks "natural" to a human observer under normal viewing conditions, as compared with lenses with longer or shorter focal lengths which produce an expanded or contracted field of view that distorts the perspective when viewed from a normal viewing distance.[1][2] Lenses of shorter focal length are called wide-angle lenses, while longer-focal-length lenses are referred to as long-focus lenses[3] (with the most common of that type being the telephoto lenses).

For still photography, a lens with a focal length about equal to the diagonal size of the film or sensor format is considered to be a normal lens; its angle of view is similar to the angle subtended by a large-enough print viewed at a typical viewing distance equal to the print diagonal;